System of refrigeration



July 3, 1928. 1,675,455

P. E. HAYNES SYSTEM OF REFRIGERATION Filed Jan 16 1924 Patented July 3, 1928.

UNITED STATES PIERRE E. HAYNES, OF EAST AURORA, NEW YORK.

SYSTEM OF REFRIGERATION.

Application filed January 16, 1924. Serial No. 686,497.

This invention relates to a system of refrigeration.

Practically all of the present refrigeration methods consist in allowing a liquid to with- 5 draw heat from its environment and be evaporated thereby. The vapor or gas formed is removed and restored to the liquid condition to be used over again. In general there are two ways of carrying out this process: Vapor may be withdrawn by a pump, compressed and cooled to the liquid condition and subsequently expanded to a lower pressure; or, the vapor may be dissolved in a suitable solvent at a lower pressureand transferred by a pump to a zone of higher pressure and temperature whereupon the vapor is driven from solution by heat, cooled, liquefied and expanded to a lower pressure. The first system is called a compression system, while the second is alluded to as an absorption system.

In both compression and absorption systems, the refrigeration is obtained by the expansion and evaporation of the liquefied re- .l.rigerative medium, the systems dillering only in the methods whereby the mediun'i is raised to the liquefying pressure. In both systems the theoretical maximum refrigeration which may be obtained is equivalent to the latent heat of evaporation of the refrigerative medium plus the sensible heat requiredto warm the refrigerative medium to the temperature of the cold absorbing me dium.

In practice, however, these prior systems are open to objection, first because of the energy cost, and second because in the tropics, where the possible uses of refrigeration are greater than in other parts of the world, and in vessels voyaging to the tropics, it has been impossible, because of limitations imposed. by the higher air and water temperatures, to use certain refrigerants, notably carbon dioxide which is particularly de- 'sirable because of its cheapness.

The present invention has for its principal object to overcome the above disadvanitages. Stated in positive terms the principal object is to provide a relatively simple system which has greater efliciency and wider utility than systems heretofore known.

The invention differs essentially from the known methods, first in that a miscible ma- 'terial capable of forming a solution with the 'refrigerative medium is added thereto with the result of increasing the critical temperature of the refrigerative medium and decreasing its critical pressure, the refrigeration is obtained by the separation of a refrigerative medium from its solvent and the cold produced is the result of the release of a gaseous material. from solution rather than the evaporation of a liquefied material as heretofore, and a part of the solution in which cold is produced is utilized to perform the work of refrigeration instead of relying on the use of a brine solution and a brine circulating system as frequently re quired in the known systems.

The present method of refrigeration may be applied to any combination of a gaseous refrigerative medium and a miscible normally liquid non-refrigerative material where the solution results in an evolution of heat and the separation results in the absorption of heat, i. e., where the heat of solution exceeds the heat of vaporization. My method consists generally in. subjecting a gaseous refrigerative medium and a miscible material capable of forming a solution therewith to suitable pressures, with possible liquefaction of the gas, in mixing the compressed refrigerative medium and miscible material and dissipating the heat of the mixture, in expanding the solution to drive off the gas, the energy being drawn from the gas and the miscible material whereby a depression of temperature is obtained, and in utilizing to create cold a supercooled residual solution of the refrigerative medium and the miscible material.

My experiments with carbon dioxide and ether may be taken as exemplary of the process in general. A mixture composed of carbon dioxide and ether vapor has a high er critical temperature and a lower critical pressure than carbon dioxide and may there fore be more easily liquefied by pressure than the gas alone. A solution of carbon dioxide and ether varies in concentration with the temperature but as long as one or the other of these materials remains liquid a solution is formed which is capable of refrigerative expansion. This mixture may be efficiently used in the tropics where the prevailing temperature conditions render it impossible to use carbon dioxide according to the methods heretofore known, and under favorable conditions of air and water, i. e., in the temperate zone, the present method and mixture may be used with greater efiiciency than the known methods.

In the broadest aspect of the invention the essential facts are that carbon dioxide and ether are combined as a mixture which is utilized as a refrigerative medium and that the ether of the mixture favorably alters the critical constants of the gas, that is to say raises its critical temperature and lowers its critical pressure. As a matter of procedure I may add compressed carbon dioxide to liquid ether or I may add ether vapor to carbon dioxide. So far as the resulting mixture is concerned it is immaterial in the broad contemplation of the in vention whether ether be the solvent and carbon dioxide be the'solute as in the first mode or whether carbon dioxide be the solvent and ether the solute as in the second mode.

The first mode of procedure is, however, preferred because of its greater eiiiciency.

Thus I have found that carbon dioxide in the liquid condition is miscible in all practical propor-tionswith ether and-that the mixing of the two results in the evolution of heat. I have further found that when the heat of solution'is dissipated and the solution brought back to a normal temperature it may be expanded and cold produced. It is well known that the energy required to raise the pressure on a liquid is far less than the energy required to raise the pressure of gases or vapors. This is because liquids are practically incompressible and the raising of the pressure does not involve serious molecular displacement as is the case with gases. It follows, therefore, that a solution of carbon dioxide and other is obtained at an energy cost only slightly in excess of that required to compress and liquefy the carbon dioxide.

I do not know the value of the heat of solution of carbon dioxide and ether but .since the addition of liquid carbon dioxide gas alone were expanded between the same 7 pressure limits.

In the practice of my method I transfer all of the cold produced to the ether and return the warm carbon dioxide directly to the compressor. This transfer may be effected by a combination of heatexchangers wherein the warm solution of carbon dioxide in ether passes in counter current and heat exchanging relation to the cold productsof expansion effervescing at the expansion value. Because the ether is cold it still holds a quantity of carbon dioxide in solution after being expanded to the lower pressure. This solution which is obtained as the product of the system is therefore a supercooled solution of carbon dioxide in ether wherein the concentration of the gas is lower than it was before it was expanded to the reduced pressure. As this cold solution is warmed incident to its work of refrigeration it releases gaseous carbon dioxide and absorbs as latent orinsensible heat the energy necessary to drive the carbon dioxide from solution. The refrigeration content ofthe ethereal solution of carbon dioxide is therefore greater than the sensible cold contentof pure ether cooled to the same temperature and the solution has the advantage of absorbing heat with a smaller rise of temperature than pure ether under the same telnperature conditions.

The characteristic temperature of a solution of carbon dioxide snow in ether is less than 100 degrees F. and with my system it is possible to obtain a steady supply of ether containing dissolved and suspended carbon dioxide at the approximate fixed temperature of carbon dioxide snow in ether. This result is obtained without danger of freezeups because the particles of carbon dioxide snow do not adhere to the expansion valve. This fact is explained by stating that the carbon dioxide is still dissolved at the higher pressure and is not precipitated until the mixture has been expanded. The amount of refrigeration which may be stored in ether in this way is considerably in excess of that in pure ether at the same low temperature.

Because carbon dioxide is relatively more soluble in ether than oxygen or nitrogen, it will be possible to use carbon dioxide from any source where the impurities are chiefly oxygen and nitrogen. 'The carbon .dioxide may be dissolved from its gaseous mixture and the undissolved gases rejected. Garbon dioxide thus formed will be relatively cheap and the necessity of preventing packing leaks on compressorparts will not be so great. The reduction of packing pressure on compressor piston rods will greatly reduce the friction on these parts with a corresponding decrease in wear and energy cost.

The ease with which my process may be controlled to give any desired temperature bet-ween those requiredfor coldstorage and the lower temperatures required for the freezing of fish and similar needs is an additional advantage. By control ,of either .high or low pressure or both any desired temperature or refrigeration requirement within the limitations of the plantmay be obtained. H

The direct utilization of the ether in the supercooled residual solution for the work of refrigeration has the advantage of eliminating the special non-freezing medium such as a solution of brine which is required in the known systems and which is circulated to the point or points where the refrigeration is required. The brine equipment is objectionable because of its intrinsic complications and its use entails an unavoidable refrigeration loss incident to the transfer of refrigeration to the brine.

The practice of the invention is illustrated by the accomymnying drawings, in which the single figure is a diagram illustrating a preferred. mode of procedure.

Av solution 1 of a gas, for example carbon dioxide, in a suitable normally liquid solvent such as ether, is contained in vessel 2. This solution passes through pipe 3 to cooling coil 4- where it is cooled by contact of coil 4 with air or water to dissipate the heat produced by dissolving of carbon dioxide in ether in vessel 2. The cooled'solution now passes in counter current and heat exchanging relation to liquid ether and gaseous carbon dioxide, the solution passing through coil 5 which is surrounded by the colder materials in vessel 6. From coil 5 the solution passes through pipe 7 to coil 8 in vessel 9 where it passes in counter current and heat exchanging relation to gaseous carbon dioxide in space 11 of vessel 9. From coil 8 the cold solution passes through expansion valve 10 in vessel 9 and emerges in space 11 at a lower pressure depending upon the temperature desired.

At this point there is a violent effervescence of carbon dioxide which leaves a cold but weaker solution of carbon dioxide in ether in the bottom of vessel 9. The effervescing dioxide passes upward around coil 8 and emerges from vessel 9 through pipe 12.

The cold solution of carbon dioxide in ether in the bottom of vessel. 9 passes to pipe 13 and from thence to coil 14 where it does refrigerating duty and is thereby warmed. The increase in temperature of the ether at this point causes the release of additional carbon dioxide gas which passes through the pipe 15 with the warmed ether to vessel 6 and around coil 5 where both are mingle with the carbon dioxide from pipe 12. The materials passing upward through vessel 6 serve to cool the warm solution passing in counter current through coil 5. A further separation of carbon dioxide takes place in vessel 6 and both gas and liquid emerge from this vessel at approximately atmospheric temperature. The warm ether passes from vessel 6 through pipe 17 to ether pump 18 where its pressure is raised to that of liquid carbon dioxide or less and from thence it passes through pipe 21 to spray head 22 in vessel 2. i

The Warm carbon dioxide emerging through pipe 16 contains ethervapor and passes to compressor 19 where it is compressed to the pressure of liquefaction or less and thence passes to condenser and accumulator 20 where it mayor may not lique fy according to the conditions of operation.

The presence of ether vapor in the carbon dioxide returned to the compressor 19 is a valuable feature of the invention, although it is not indispensable in its broadest aspects. The advantage of the ether vapor in mixture with the warm carbon dioxide is that thereby the critical temperature of the gas is increased and its critical pressure reduced. From condenser or accumulator 20 the carbon dioxide passes to vessel 2 and emerges beneath the surface of the ether in vessel 2 previously mentioned.

The leakage of carbon dioxide is made up in the following manner: A carbonaceous material, for example, illuminating gas, is drawn from pipe 23 and burned in burner 24 surrounded by vessel 25. The products of combustion are drawn as needed into the suction pipe of compressor 19 through pipe 26. The combustion mixture contains oxygen, nitrogen, and carbon dioxide and mingles with carbon dioxide previously formed and is raised to a high pressure. W hen this mixture roaches vessel 2 the carbon dioxide is separated by being dissolved in the ether while the unabsorbed gases escape from vessel 2 by means of valve 27.

\Vhile I have specifically mentioned a mixture of carbon dioxide and ether it will be understood that the invention is not limited to these ingredients but contemplates any mixture of a suitable aseous refrigerative medium and a normally liquid miscible nonrefrigerative material wherein the solution results in an evolution ofheat and the separation results in the absorption of heat.

Having fully described my invention, I claim:

In a system of refrigeration, incorporating with a compressed gaseous refrigerative medium a normally liquid miscible non-refrigerative material capable of entering into so lution with the medium and of raising the critical temperature and lowering the critical pressure of the medium, the heat of solution exceeding the heat of vaporization, cooling and reducing the pressure of the mixture whereby the gaseous medium is driven out of the solution and a super-cooled residue of the solution with a weak concentration of the refrigerative medium remains, utilizing said residue for the work of refrigeration, compressing and cooling the medium, and circulating the medium and ma terial in a continuing cycle.

In testimony whereof I afiix my signature,

PIERRE E. HAYNES.

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